#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
const int mod = 1e9 + 7;

int gcd(int a, int b)
{
    return b ? gcd(b, a % b) : a;
}

ll qmi(ll a, ll b)
{
    ll res = 1;
    while(b)
    {
        if(b & 1)res = res * a % mod;
        b >>= 1;
        a = a * a % mod;
    }
    return res;
}
struct custom_hash {
	static uint64_t splitmix64(uint64_t x) {
		x ^= x << 13;
		x ^= x >> 7;
		x ^= x << 17;
		return x; 
	}
	size_t operator () (uint64_t x) const {
		static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count(); // 时间戳
		return splitmix64(x + FIXED_RANDOM);
	}
};

void solve()
{
    int n, x;
    cin >> n >> x;
    vector<int> a(n);
    map<int, int> mp;
    for(int i = 0; i < n; i++){
        cin >> a[i];
        mp[a[i]]++;
    }
    map<int, int> cnt;
    for(int i = 0; ; i++)
    {
        if(mp[i])
        {
            mp[i]--;
            cnt[i % x] += mp[i];
        }
        else if(cnt[i % x])
        {
            cnt[i % x]--;
        }
        else{
            cout << i << endl;
            return;
        }
    }
    

}

int main()
{
    int t = 1;
    cin >> t;
    while(t--)
        solve();
    return 0;
}